Fortran: implement free & fixed formats

Summary:
FEATURE: 372950

Task T9775

* Implement patch provided at: https://github.com/janusw/syntax-highlighting/commits/Fortran_2003_2008
* The `fortran-fixed.xml` file corresponds to the original file (`fortran.xml`), which is renamed. The `fortran-free.xml` file uses `IncludeRules` and include-keywords to avoid replicated code.
* Some unnecessary `RegExpr` rules are replaced for optimization.

TODO: ask for MIT license.

Reviewers: #framework_syntax_highlighting, dhaumann, cullmann

Reviewed By: #framework_syntax_highlighting, cullmann

Subscribers: nononux, kwrite-devel, kde-frameworks-devel

Tags: #kate, #frameworks

Differential Revision: https://phabricator.kde.org/D21713